The present invention relates to a water turbine arrangement comprising a generator enclosed in a cylindrical casing and a turbine arranged directly on a generator shaft, outside the casing, the casing being arranged to a flow conduit by means of a support structure comprising a tubular support shaft arranged to carry the cylindrical casing in the flow conduit.
Water turbines are commonly used for producing electric energy at power plants typically located at river beds or other places where the necessary water head or flow rate can be obtained. At water-power plants, a generator rotated by a water turbine converts kinetic or potential energy of water into electricity. The water flow acts on the turbine blades, thereby causing a rotating movement in the turbine and in the generator coupled to the turbine.
Prior art knows various different types of water turbines, suitable for water flows and heads of different sizes. The turbines differ from one another, for example, in the form of the turbine blades and their adjustability, and in the generator location and its installation position. The most commonly used generator is a synchronous machine directly connected to a network into which energy is to be supplied. The generator must then be made to rotate at a predetermined speed corresponding to synchronous speed determined by the network frequency and the generator""s pole pair number. The correct rotation speed is most often obtained by means of a gearing arranged between the turbine and the generator, the gearing being conventionally used for increasing the rotation speed of the generator. Increased rotation speed allows the pole pair number and, at the same time, the diameter of the synchronous machine to be reduced. However, the gearing needed to change the rotation speed causes a significant portion of the power plant""s losses. Moreover, the generator and the gearing require a cooling equipment for transferring the heat that is generated in the gearing. For practical reasons, the gearing must be located on the shaft coupling the generator and the turbine, therefore large plant premises are needed. In addition, for any servicing of the generator or the gearing, area for service aisles must be reserved at the plant.
With current arrangements, the costs of building water-power plants at dams are considerably high. A water turbine and the related components, such as the gearing and the generator, are also difficult to install to dam constructions. At some plants, the gearing and the generator directly connected to the network are both placed into the same cylindrical casing located in the flow conduit. An example of this solution is the bulb-generator. The casing enclosing the generator and the gearing is rather big, which means that the support structures carrying the casing also need to be big. There must also be enough room to allow any maintenance works to be carried out inside the casing.
In certain solutions, the generator and the gearing are placed outside the flow conduit, the flow conduit then incorporating only the turbine and the support structure carrying it. The turbine shaft must be applied through the wall of the flow conduit and sealed therein, the gear and the generator thus requiring separate premises at the plant construction, in the vicinity of the flow conduit.
The turbine must be installed into the flow conduit with great care, and it must be aligned precisely with the flow conduit. The installation is difficult-because the space where the turbine is to be placed is small, and the size and weight of the equipment to be installed is large.
An object of the present invention is to provide a water turbine arrangement that avoids the above-mentioned shortcomings and simplifies the constructions of equipment associated with water-power plants, thereby facilitating installation works at the plants. This object is achieved with an arrangement of the invention characterized in that the cylindrical casing comprising the generator, together with the tubular support shaft and the turbine, are arranged to be removed from the flow conduit as a single piece through an installation hole.
The invention is based on the idea that the generator being enclosed in a casing which is carried by the support shaft and installed into the flow conduit in such a way that the turbine, which is coupled to the generator by means of a shaft, is positioned precisely in the flow conduit. The cylindrical casing only comprises the generator and parts directly relating thereto, the outer dimensions of the casing thus being as small as possible and the installation as simple as possible.
An advantage of the invention is that it considerably simplifies the installation of a water turbine arrangement. The installation can be carried out through an installation hole, with the turbine already coupled to the generator. Through the installation hole, the cylindrical casing comprising the generator can be aligned with the flow and the flow conduit into precisely right position. In addition, the tubular support shaft carrying the casing in the flow conduit is particularly well suited for housing the generator cabling and the generator cooling air ducts.